In a television system adopting composite video broadcast signal (CVBS) or video graphics array (VGA) standard, signals are fed into an integrated circuit through AC coupling capacitors, and an input stage is generally implemented by source followers to provide driving ability and high input impedance. However, an input DC level of the source follower is generally determined by a clamping circuit but an output DC level is not well defined, causing worse linearity of the signal path and potential reliability issue if low-voltage devices are used in succeeding circuits.